Effective, Shortened Drying of Agar-Gelcasting Al2O3 Tube Through Immersing in Acetone
Abstract A liquid drying agent, i.e. acetone, was employed for allowing the faster drying of Al2O3 tubes fabricated by agar gelcasting than the conventional air drying. The mixture of Al2O3 slurry and agar solution was separately prepared and then mixed prior to molding out of a set of warmed glass tubes. After the mixture transformed into gelled tube, the gelled tube was demolded and then immersed in acetone at different periods of time from 0 to 50 h. The immersed periods of 50 h led to the acetone replacement for water being inside of the gelling tube by 74 wt.% and then shortened the drying period to be 25 min. On the other hand, the conventional air drying spent 420 min drying completely. After drying, the immersed tubes possessed spherical cross section; whereas, no immersed tubes showed the deformation of cross section. The shortened drying was in line with the smaller drying shrinkage (4.7%), broader pore-size distribution and higher porous microstructure, comparing to the conventional air drying. The mechanism of acetone replacement for water was attributed to the acetone-water concentration gradient creating their inter-diffusion.